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Tubes for PAS 3+ and Mark III

67.212.99.88
Posted on January 20, 2019 at 05:34:37
Gt6mark1@gmail.com
Audiophile

Posts: 3
Location: IA
Joined: January 20, 2019
 I believe the PAS3+ came with 12AX7 and the Mark III came with KT88. Want to replace them with new tubes and looking for suggestions. I prefer a warm, fat, bass over brightness. Iv;e heard the Gold Lion re-issues are good?

Appreciate your help.

 

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RE: Tubes for PAS 3+ and Mark III, posted on January 20, 2019 at 10:07:52
petercapo
Audiophile

Posts: 665
Joined: December 29, 2012
 Assuming your Dynacos are in their original configuration, yes the PAS uses four 12AX7 and one 12X4 rectifier. The Mark III uses one 6AN8, one 5AR4 and two 6550 or KT88 per monoblock.

For the PAS phono section, consider the Sovtek 12AX7LPS that is said to be quiet. For warmer and fatter, try the Mullard 12AX7 reissues.

Yes, the GL KT88 is a really nice tube, but for something warmer and fatter, the current production Svetlana 6550 (not Winged =C=, not old production Svetlana types) comes to mind.

Changing tubes is fine but don't overlook the health of the PAS and Mark III. The manual for each contains a chart of reference voltages for different nodes in their circuits. Checking yours against those standard values is a worthwhile exercise

 

RE: Tubes for PAS 3+ and Mark III, posted on January 20, 2019 at 11:01:00
tubular.well
Dealer

Posts: 223
Joined: March 4, 2013
 It's unlikly that the tubes in PAS needs to be changed. Keep them unless there is a problem.
The MkIII however needs 6550 / KT88 now & then , be shure to but a maxed pair, or even better buy a matched quad.
As for brands to use, i have good experience with JJ 6550, but any decent brand shoud work. Best is to buy them from a reputable dealer that will
be available newxt week and who also warrants the tubes.

 

Good advice, all the way around (nt), posted on January 20, 2019 at 11:06:58
1973shovel
Audiophile

Posts: 10117
Location: Greenville SC
Joined: February 25, 2007

 

RE: Tubes for PAS 3+ and Mark III, posted on January 21, 2019 at 15:34:33
Gt6mark1@gmail.com
Audiophile

Posts: 3
Location: IA
Joined: January 20, 2019
 The new Svetlana 6550 are all 6550C, unless I misunderstood your post? Is 6550C ok?
As far as 12X4, 6AN8, and 5AR4 do you have any specific recommendations?
The Mark 3s have been gone through. I definitely need to give the PAS3+ some love. I Deoxed the pots, one of the tone pots is bad. The on/off switch is shot. Not sure about the source selector switch seems like there's crosstalk over what's selected (if you have an LP on the phono you can kinda hear it if another input is selected. Which of the four tubes are the phono stage?. I struggle a little as you could literally replace everything and IMO lose some of the romance of the old girl. I'd like to do a restoration and replace what I need to instead of everything. Then maybe just build one of the new pre-amps.

 

RE: Tubes for PAS 3+ and Mark III, posted on January 21, 2019 at 16:50:38
petercapo
Audiophile

Posts: 665
Joined: December 29, 2012
 The new Svetlana 6550 are all 6550C, unless I misunderstood your post? Is 6550C ok?
Yes, I believe it is marked 6550C.

As far as 12X4, 6AN8, and 5AR4 do you have any specific recommendations?
Any 12X4 should do. Any 6AN8 should do. For the 5AR4, I'd go with the newer Gold Lion.

The Mark 3s have been gone through.
What kind of work was done?

I definitely need to give the PAS3+ some love. I Deoxed the pots, one of the tone pots is bad. The on/off switch is shot. Not sure about the source selector switch seems like there's crosstalk over what's selected (if you have an LP on the phono you can kinda hear it if another input is selected.
Crosstalk is common in the PAS.
Here is something you might be interested in reading: PAS Low Cost Refresh
With regard to spraying pots, selector switches or anything containing a phenolic material, I'd recommend reading through the entire thread here and here.

Which of the four tubes are the phono stage?.
Two 12AX7 in phono stage, two 12AX7 in the line stage. The phono board is the one closer to the selector switch.

I struggle a little as you could literally replace everything and IMO lose some of the romance of the old girl. I'd like to do a restoration and replace what I need to instead of everything.
There's no substitute for familiarizing yourself with your Mark III and PAS. If you do not already have them, download a copy of the original Dynaco manuals preferably including the original pictorial wiring diagrams and study it all. You will never know what your Mark IIIs and PAS are capable of unless they are in proper working order. Don't be in too much of a rush to replace the tubes, either. Do you know for a fact that the tubes in there now are no good?

Then maybe just build one of the new pre-amps.
IMO if your PAS is working to its potential, you may not want a different preamp.


Again, everything I have been posting assumes your Mark IIIs and PAS are in their original configurations. If not, all bets are off.

 

My favorite audiophile faux pas, posted on January 25, 2019 at 05:36:49
1973shovel
Audiophile

Posts: 10117
Location: Greenville SC
Joined: February 25, 2007
 "be shure to"

Reading this always makes me smile, and I've spelled it that way a time or two myself!

 

PAS, JJ803S, MKiii, Winged C 6550 or GL KT88. nt, posted on January 31, 2019 at 14:46:20
viridian
 Nt

 

RE: Tubes for PAS 3+ and Mark III, posted on February 2, 2019 at 07:07:04
xaudiomanx
Audiophile

Posts: 3647
Joined: August 16, 2004
 Along with other advice Jim McShane is a good reference for tubes as well. He, like others, is very knowledgeable and never steered me wrong.

 

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